Active video projection screen

ABSTRACT

Instead of a monochromatic projection screen, an active projection screen is provided which varies reflectance and gray level (black to white) in synchronization with the content being shown. Groups of multiple screen pixels, which are smaller than each projected pixel from the projector, are assigned to each respective larger projection pixel.

FIELD

The application relates generally to video projection screens.

BACKGROUND

Television designers have gone to great lengths to control the backlightlevel even going so far as to provide per pixel backlight control forliquid crystal display (LCD) televisions. At the same time, the amountof light emitted by the television has increased dynamically. Couplingthis large increase in both contrast and brightness with moving to tenbits per color component (over the eight bits previously used) createswhat is termed “High Dynamic Range” content.

Because of the monochromatic nature of projection screens, it has beendifficult to realize HDR content through a projector system.

SUMMARY

As understood herein, the refresh rate for e-ink projection systems hasbecome nearly comparable to video displays. In an embodiment, aprojection screen has a large array (or set of arrays) of e-ink paper.The pixel size on the screen coming from the projector is larger thanthe size of an individual element of e-ink. For example, a thirty footwide screen showing a 4K ultra high definition (UHD) can receiveprojected pixels roughly one tenth of an inch wide. Depending on thecurvature of the movie screen and the projection lenses, the size of thepixels will vary slightly across the screen and there may be a slightalignment distortion. Understanding that the pixel size from theprojector is larger than the e-ink element size in the screen, an areais established that can display a smooth range of grayscale values thatgo from pure black to pure white. By having multiple e-ink elements(each either being black or white), gray scale levels can be establishedusing, e.g., stippling techniques. Also, because each individual e-inkelement of the projection screen can be individually addressed, thereflective areas of the screen can be aligned per pixel to locations ofthe pixels sent from the projector.

In an embodiment, the e-ink elements on the active projection screen canbe aligned/calibrated to projected pixels using a grid projected ontothe screen from the projector. The purpose of using a grid system toalign the pixels with the projection system is to calibrate the screenand define which pixel on the screen is assigned with the correspondingpixels from the projection system.

Consequently, areas of the content meant to appear bright will be verybright and area of the content meant to be dark will be very dark with asmooth, continuous gradation between the two. Furthermore, given thatsome movie projection systems are running at rates much higher thancurrent e-ink might allow, the e-ink based projection screen may beoperated at thirty Hz while the projector can be operated at 60 Hz (orhigher).

Accordingly, an apparatus includes at least one computer memory that isnot a transitory signal and that includes instructions executable by atleast one processor to establish, for at least some pixels of at leastsome frames of a color video file, respective grayscale values. Theinstructions are executable to, using each one of at least some of thegrayscale values, establish plural screen pixel control values. Eachscreen pixel control value defines whether an associated screen pixel isto be configured to present a white appearance or a black appearance.Thus, each of at least some pixels in the color video file is associatedwith plural screen pixel control values. The instructions are alsoexecutable to arrange the grayscale values and/or the screen pixelcontrol values in a grayscale file in synchronization with the frames ofthe color video file from whence the grayscale values were derived.Furthermore, the instructions are executable to render the color videofile accessible for projection onto an active screen, and to render thegrayscale file accessible to the active screen for control of screenpixels in the active screen responsive to the screen pixel controlvalues.

In some embodiments, the screen pixel control values for each grayscalevalue are established using a stippling-like technique. The grayscalefile and color video file both can be sourced from a single source. Or,the color video file can be sent from a first source to a projector forprojection onto the active screen, and the grayscale file can be sentfrom a second source to the active screen.

In example implementations, the grayscale values are established usingluminance information in the color video file. The instructions may beexecutable for establishing, for all pixels of at least some frames ofthe color video file, respective grayscale values, and using each one ofall of the grayscale values to establish plural screen pixel controlvalues. The active screen can be an e-ink screen.

In another aspect, an apparatus includes at least one computer memorythat is not a transitory signal and that includes instructionsexecutable by at least one processor to associate respective groups ofplural screen pixels in an active screen with respective individualcolor pixels from a projector to be projected onto the active screen,and in synchronization with projection of the color pixels onto theactive screen, to control the respective plural screen pixels of each ofat least some of the respective individual color pixels to establish ademanded grayscale on the active screen.

In examples of this latter aspect, the instructions can be executable toestablish, for at least some pixels of at least some frames of a colorvideo file, respective grayscale values, and using each one of at leastsome of the grayscale values, establish plural screen pixel controlvalues. Each screen pixel control value defines whether an associatedscreen pixel is to be configured to present a white appearance or ablack appearance, such that each of at least some pixels in the colorvideo file is associated with plural screen pixel control values. Theinstructions may be further executable to arrange the grayscale valuesand/or the screen pixel control values in a grayscale file insynchronization with the frames of the color video file from whence thegrayscale values were derived. Moreover, the example instructions can beexecutable to render the color video file accessible for projection ontothe active screen, and to render the grayscale file accessible to theactive screen for control of screen pixels in the active screenresponsive to the screen pixel control values.

In further examples, the screen pixel control values for each grayscalevalue can be established using a stippling-like technique. The grayscalevalues can be established using luminance information in the color videofile.

Example instructions may be executable to associate the respectivegroups of plural screen pixels in the active screen with the respectiveindividual color pixels by projecting at least one column and/or row ofcolor pixels onto the screen, and activating at least plural columnsand/or rows of screen pixels. These instructions may be furtherexecutable to, based on at least one image of the at least one columnand/or row of color pixels projected onto the screen over activatedcolumns and/or rows of screen pixels, associate respective groups ofplural screen pixels with the respective individual color pixels. Theinstructions can be executable to align at least one edge of at leastone frame of color pixels with at least one corresponding edge of theactive screen.

In another aspect, a method includes associating plural screen pixelswith respective individual pixels to be projected. The method alsoincludes projecting the pixels to be projected onto an active screenassociated with the screen pixels to produce a demanded color image, andcontrolling the screen pixels to produce a demanded grayscale backgroundderived from the respective pixels to be projected.

The details of the present application, both as to its structure andoperation, can best be understood in reference to the accompanyingdrawings, in which like reference numerals refer to like parts, and inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example system including an example inaccordance with present principles;

FIG. 2 is a schematic view of the projection screen showing largerprojected pixels superimposed on groups of smaller screen pixels toillustrate that each projected pixel is associated with a respectivegroup of screen pixels;

FIG. 3 is a schematic view of the projection screen illustrating anexample alignment initialization process, in which one or more edges ofthe projected pixel footprint are aligned with respective edges of thescreen;

FIG. 4 is a schematic view of the projection screen illustrating anexample alignment process, in which a mapping of the association of thescreen pixels to projected pixels is generated; and

FIG. 5 is a flow chart of example logic.

DETAILED DESCRIPTION

This disclosure relates generally to computer ecosystems includingaspects of consumer electronics (CE) device networks such as projectorsystems. A system herein may include server and client components,connected over a network such that data may be exchanged between theclient and server components. The client components may include one ormore computing devices including video projectors and projector screens,portable televisions (e.g. smart TVs, Internet-enabled TVs), portablecomputers such as laptops and tablet computers, and other mobile devicesincluding smart phones and additional examples discussed below. Theseclient devices may operate with a variety of operating environments. Forexample, some of the client computers may employ, as examples, operatingsystems from Microsoft, or a Unix operating system, or operating systemsproduced by Apple Computer or Google. These operating environments maybe used to execute one or more browsing programs, such as a browser madeby Microsoft or Google or Mozilla or other browser program that canaccess web applications hosted by the Internet servers discussed below.

Servers and/or gateways may include one or more processors executinginstructions that configure the servers to receive and transmit dataover a network such as the Internet. Or, a client and server can beconnected over a local intranet or a virtual private network. A serveror controller may be instantiated by a game console such as a SonyPlaystation (trademarked), a personal computer, etc.

Information may be exchanged over a network between the clients andservers. To this end and for security, servers and/or clients caninclude firewalls, load balancers, temporary storages, and proxies, andother network infrastructure for reliability and security. One or moreservers may form an apparatus that implement methods of providing asecure community such as an online social website to network members.

As used herein, instructions refer to computer-implemented steps forprocessing information in the system. Instructions can be implemented insoftware, firmware or hardware and include any type of programmed stepundertaken by components of the system.

A processor may be any conventional general purpose single- ormulti-chip processor that can execute logic by means of various linessuch as address lines, data lines, and control lines and registers andshift registers.

Software modules described by way of the flow charts and user interfacesherein can include various sub-routines, procedures, etc. Withoutlimiting the disclosure, logic stated to be executed by a particularmodule can be redistributed to other software modules and/or combinedtogether in a single module and/or made available in a shareablelibrary.

Present principles described herein can be implemented as hardware,software, firmware, or combinations thereof; hence, illustrativecomponents, blocks, modules, circuits, and steps are set forth in termsof their functionality.

Further to what has been alluded to above, logical blocks, modules, andcircuits described below can be implemented or performed with one ormore general purpose processors, a digital signal processor (DSP), afield programmable gate array (FPGA) or other programmable logic devicesuch as an application specific integrated circuit (ASIC), discrete gateor transistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. A processorcan be implemented by a controller or state machine or a combination ofcomputing devices.

The functions and methods described below, when implemented in software,can be written in an appropriate language such as but not limited to C#or C++, and can be stored on or transmitted through a computer-readablestorage medium such as a random access memory (RAM), read-only memory(ROM), electrically erasable programmable read-only memory (EEPROM),compact disk read-only memory (CD-ROM) or other optical disk storagesuch as digital versatile disc (DVD), magnetic disk storage or othermagnetic storage devices including removable thumb drives, etc. Aconnection may establish a computer-readable medium. Such connectionscan include, as examples, hard-wired cables including fiber optics andcoaxial wires and digital subscriber line (DSL) and twisted pair wires.Such connections may include wireless communication connectionsincluding infrared and radio.

Components included in one embodiment can be used in other embodimentsin any appropriate combination. For example, any of the variouscomponents described herein and/or depicted in the Figures may becombined, interchanged or excluded from other embodiments.

“A system having at least one of A, B, and C” (likewise “a system havingat least one of A, B, or C” and “a system having at least one of A, B,C”) includes systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, etc.

Now specifically referring to FIG. 1, an example ecosystem 10 is shown,which may include one or more of the example devices mentioned above anddescribed further below in accordance with present principles. The firstof the example devices included in the system 10 is a projection screenassembly 12. The projection screen assembly 12 can be established bysome or all of the components shown in FIG. 1. The projection screenassembly 12 includes an active display or screen in that it containsaddressable screen elements that establish screen pixels and that can becontrolled to establish grayscale values as demanded by a video file tobe shortly disclosed.

For example, the projection screen assembly 12 can include one or moree-ink type screens or displays 14 that may be implemented by one or moree-ink arrays. An e-ink array may be made of small polyethylene spheres(for instance, between seventy five and one hundred micrometers indiameter). Each sphere may be made of negatively charged black plasticon one side and positively charged white plastic on the other. Thespheres can be embedded in a transparent silicone sheet, with eachsphere suspended in a bubble of oil so that it can rotate freely. Thepolarity of the voltage applied to each pair of electrodes thendetermines whether the white or black side is face-up, thus giving thepixel a white or black appearance. Other e-ink technology may usepolyvinylidene fluoride (PVDF) as the material for spheres. Other e-inktechnologies includes electrophoretic with titanium dioxide particlesapproximately one micrometer in diameter dispersed in a hydrocarbon oil,Microencapsulated Electrophoretic Displays, electrowetting,electrofluidic, and interferometric modulator displays that can createvarious colors using interference of reflected light, bistable displayssuch as flexible plastic electrophoretic displays, cholesteric liquidcrystal displays, nemoptic displays made of nematic materials organictransistors embedded into flexible substrates, electrochromic displays,etc.

Other active screen technology that may be used include “metamaterials”, chemical-based active screens, and screens with pixelsestablished by carbon nanotubes.

The projection screen assembly 12 may include one or more speakers 16for outputting audio in accordance with present principles, and at leastone input device 18 such as e.g. an audio receiver/microphone or key pador control keys for e.g. entering commands to at least one screenprocessor 20. The example screen assembly 12 may also include one ormore network interfaces 22 for communication over at least one network24 such as the Internet, an WAN, an LAN, etc. under control of the oneor more processors 20. Thus, the interface 22 may be, withoutlimitation, a Wi-Fi transceiver, which is an example of a wirelesscomputer network interface, such as but not limited to a mesh networktransceiver, or it may be a Bluetooth or wireless telephony transceiver.It is to be understood that the processor 20 controls the screenassembly 12 to undertake present principles, including the otherelements of the screen assembly 12 described herein such as e.g.controlling the display 14 to present images thereon and receiving inputtherefrom. Furthermore, note the network interface 22 may be, e.g., awired or wireless modem or router, or other appropriate interface suchas, e.g., a wireless telephony transceiver, or Wi-Fi transceiver asmentioned above, etc.

In addition to the foregoing, the screen assembly 12 may also includeone or more input ports 26 such as, e.g., a high definition multimediainterface (HDMI) port or a USB port to physically connect (e.g. using awired connection) to another CE device and/or a headphone port toconnect headphones to the screen assembly 12 for presentation of audiofrom the screen assembly 12 to a user through the headphones. Forexample, the input port 26 (and/or network interface 22) may beconnected via wire or wirelessly via the network 24 to a cable orsatellite or other audio video source 28 with associated sourceprocessor 28A and source computer memory 28B. Thus, the source may be,e.g., a separate or integrated set top box, or a satellite receiver. Or,the source 28 may be a game console or personal computer or laptopcomputer or disk player. Yet again, the source 28 and/or the color videosource discussed below may be cloud servers on the Internet, and mayinclude and perform “cloud” functions such that the devices of thesystem 10 may access a “cloud” environment via the server 28 in exampleembodiments. Or, the server 28 may be implemented by a game console orother computer in the same room as the other devices shown in FIG. 1 ornearby.

In any case, the video source 28 controls the reflectance of the videoshown on the screen assembly 12 by the below-described projector byinputting grayscale values to the active pixels of the screen assembly12. The video source 28 may be a separate video source as shown whichreceives full color video and derives a grayscale rendering thereofaccording to principles discussed below, in which case the source 28 istailored to source a separate piece of grayscale content to maximize theusage of the reflectance properties of the screen assembly 12. Such asource 28 may be separate from the screen assembly 12 as shown or it maybe incorporated into the screen assembly 12 in some implementations.

Or the source 28 may be the same as the color video source mentionedbelow, in which case the color video source may include a color videofile for projection onto the screen assembly 12 and a correspondinggrayscale video file that is sent to the screen assembly 12 to controlthe active elements in the screen assembly 12.

The screen assembly 12 may further include one or more computer memories30 such as disk-based or solid state storage that are not transitorysignals, in some cases embodied in the chassis of the screen asstandalone devices or as a personal video recording device (PVR) orvideo disk player either internal or external to the chassis of the AVDDfor playing back AV programs or as removable memory media.

Still referring to FIG. 1, in addition to the AVDD 12, the system 10 mayinclude one or more other device types. When the system 10 is a homenetwork, communication between components may be according to thedigital living network alliance (DLNA) protocol. Or, the projector andscreen can be used in a public movie theater.

In one example, a front projector 32 may be used to project demandedimages onto the front of the display 14. The example projector 32 mayinclude one or more network interfaces 34 for communication over thenetwork 24 under control of one or more projector processors 36. Thus,the interface 34 may be, without limitation, a Wi-Fi transceiver, whichis an example of a wireless computer network interface, including meshnetwork interfaces, or a Bluetooth transceiver, or a wireless telephonytransceiver.

It is to be understood that the projector processor 36 controls theprojector 32 to undertake present principles. In this regard, theprojector processor 36 may receive signals representing demanded colorimages from a color video source 38 which may be the same as ordifferent from the video source 28 described previously and which may beestablished by any one or more of the source types described previously.When separate grayscale and color sources are used, as opposed toseparate grayscale and color video files on the same source, the sources28, 38 may communicate with each other, e.g., via a wired communicationpath or via the network 24 as shown.

The projector processor 36 controls a lamp assembly 40 to project colorlight onto the screen assembly 12. The lamp assembly may be a laser lampassembly or other type of color illuminator assembly. The projector mayfurther include one or more computer memories 42 such as disk-based orsolid state storage.

FIG. 2 illustrates that each of at least some and more typically all ofthe full color projection pixels 200 that are projected onto the screen14 by the projector 32 is superimposed on a respective group of multiplesmaller screen pixels 202. The screen pixels 202 are the activeaddressable elements of the active screen, e.g., e-ink globes. Thus, theprojected pixels 200 that establish the color video images are largerthan the active pixels 202 within the screen 14. In the example shown,four screen pixels 202 are correlated to a single projected pixel 200,although different numbers of screen pixels 202 may be correlated to theprojected pixels 200. Note that depending on screen curvature and otherfactors as discussed below, while each projected pixel 200 typicallyoverlaps multiple screen pixels 202, the number of screen pixels 202assigned to a first projected pixel 200 may not be the same as thenumber of screen pixels 202 assigned to a second projected pixel 200.

In the example shown, the projected pixels 202 are illustrated asrectilinear areas that border each other across the entirety of thescreen 14. In implementation the shape of each projected pixel 202 maynot be precisely rectilinear owing to bleed over of light caused byreflection and other effects including lens structure on the projector32, but present principles understand that such bleed over betweenadjacent projected pixels 200 is minimized owing to the grayscalecontrol afforded by control of the screen pixels 202 described below.Also, in implementation the footprint of the combined projected pixels200 that establish the color video image may not be exactly coterminouswith, and may be smaller than, the entire active area of the screen 14,in which case FIG. 2 illustrates only the region of the active portionof the screen 14 onto which the color image is projected.

FIG. 3 illustrates an example alignment initialization process of acalibration process for assigning groups of screen pixels to individualprojected pixels. In some implementations, the edges of the projectedimage from the projector 32 are first aligned with edges of the activearea of the screen 14. In the example shown, a left-most column 300 ofprojected pixels 200 can be projected onto the screen 14. A calibrationcamera 302 may capture the image of the column 300. The calibrationcamera 302 can be controlled by a processor 304.

Based on the image from the calibration camera 302, the optics of theprojector 32 and/or the direction in which the projector 32 is pointedand/or the distance at which the projector 32 is from the screen 14 canbe modified to align the left-most column 300 with the left edge 306 ofthe active portion of the screen 14 as shown, with the left edge beingmade more visibly manifest by causing the left-most one, two, or threecolumns of screen pixels 202 to be all white. The projector 32 may bemoved left or right by hand by a person observing the image of thecolumn 300 and/or the column 300 itself as it appears on the screen. Or,the processor 304 may receive the image of the column 300 and control amotor 308 (such as a servo or stepper motor or other appropriateapparatus) to move the optics and/or housing of the projector 32 toalign the column 300 with the left edge 306.

Note that in some implementations, the left most column 300 may not bealigned with the left edge 306 of the active portion of the screen butrather with a column of screen pixels 202 that is inboard of the leftedge and thereafter regarded as a virtual left edge by the system.

It may also be desirable to align the projector 32 with the top edge 310of the screen 14, with the top edge being made more visibly manifest ifdesired by causing the top-most one, two, or three rows of screen pixels202 to be all white. In the example shown, a top-most row 312 ofprojected pixels 200 can be projected onto the screen 14. Thecalibration camera 302 may capture the image of the row 312.

Based on the image from the calibration camera 302, the optics of theprojector 32 and/or the direction in which the projector 32 is pointedand/or the distance at which the projector 32 is from the screen 14 canbe modified to align the top-most row 312 with the top edge 310 of theactive portion of the screen 14 as shown. The projector 32 may be movedhand by a person observing the image of the row 312 and/or looking atthe row 312 itself as it appears on the screen. Or, the processor 304may receive the image of the row 312 and control the motor 308 to movethe optics and/or housing of the projector 32 to align the row 312 withthe top edge 310.

Note that in some implementations, the top most column 312 may not bealigned with the top edge 310 of the active portion of the screen butrather with a column of screen pixels 202 that is below the top edge andthereafter regarded as a virtual top edge by the system. Note furtherthat the edges 306, 310 may alternatively be the physical edges of thescreen if desired, when the physical edges are not coterminous with theedges of the active portion of the screen.

If desired, once the left and top rows of projected are aligned with theleft and top edges as described, the right and bottom projected pixelcolumn/row may be aligned with the respective edges of the screenaccording to the algorithm above by, e.g., expanding or shrinking thefootprint of the projected image using, e.g., the optics of theprojector or by other means. Or, once the first two edges are aligned,the remaining two edges of the projected image may be projected onto thescreen with the underlying screen pixels thus being designated as thevirtual right and bottom edge of the screen for calibration purposes.

Present principles recognize that rows and columns of screen pixels 202may not be precisely linear. For example, the screen 14 may bedeliberately configured to be mildly concave, and/or local artifactsmight exist to introduce non-linearity. Accordingly, FIG. 4 illustratesthat once the projector 32 is aligned with the physical or virtual edgesof the screen 14, groups of screen pixels 202 may be associated withrespective projected pixels 200 so that when color video is projectedonto the screen by means of the projected pixels 200, the grayscale ofthe respective screen area onto which each projected pixel is directedis established by the screen pixels associated with that projected pixelaccording to disclosure below, even in the presence of non-linearities.

For illustration purposes, FIG. 4 assumes that each projected pixel 200encompasses an on-screen area in which three columns and two rows ofscreen pixels 202 are present. Thus, each of at least some, and in mostcases all, of the projected pixels 200 is associated with plural (e.g.,six) screen pixels 202. As shown, a column of projected pixels 200 maybe projected onto the screen 14. It is to be understood that the processof FIG. 4 can start with the left-most column, working right. Rows mayalso be aligned according to the algorithm described herein, top tobottom. Or, a grid of projected pixels may be projected onto the screen,combining column alignment and row alignment in a consolidated process.

For simplicity of disclosure, a single column 400 of projected pixels200 ₁-200 ₇ is shown and screen assignment discussed for the pixels inthat column. FIG. 4 shows five columns 202A, 202B, 202C, 202D, 202E ofscreen pixels with the three left-most columns 202A-C initially beingassigned to the column 400 of projected pixels. Candidate columns ofscreen pixels may be “illuminated” for calibration purposes by, e.g.,causing the pixels in the candidate columns all to assume the whiteconfiguration.

FIG. 4 illustrates that the columns 202A-E are not linear, with theleft-most column 202A moving out of the projected column 400 and thefourth column 200D moving into the projected column 400 beginning at thethird projected pixel 200 ₃. The screen pixel columns shift back rightby one pixel beginning at the sixth projected pixel 200 ₆. The alignmentset up in FIG. 4 may be imaged by the calibration cameras shown in FIG.3, for example, with the calibration image being sent to one or more ofthe above-described processors for image analysis to note theabove-described non-linearity of the screen pixel columns.

In the example shown, the first, second, sixth, and seventh projectedpixels 200 ₁, 200 ₂, 200 ₆, 200 ₇ would be associated with screen pixelsin the respective row of the respective projected pixel from the firstthrough third columns 202A, 202B, 202C of screen pixels based on, e.g.,imaging the presence of those screen pixels within the respectiveprojected pixels, with screen pixels in other candidate columns notbeing associated with these respective projected pixels. In contrast,the third, fourth, and fifth projected pixels 200 ₃, 200 ₄, 200 ₅ wouldbe associated with screen pixels in the respective row of the respectiveprojected pixel from the second through fourth columns 202B, 202C, 202Dof screen pixels. The process may continue using successive columns andthen rows (or using a grid as mentioned above) of projected pixels toassociate respective groups of screen pixels 202 with each respectiveone of at least some and preferably all projected pixels 200 whileaccounting for possible non-linearities in the screen 14.

Now referring to FIG. 5, the overall logic of example implementationsmay be seen. At block 500 screen pixel groups are associated with eachindividual projected pixel according to the algorithms described above.Thus, each one of some or all of the color pixels in a color video fileto be projected is associated with a respective plurality of screenpixels.

The grayscale value to be established by the screen pixels associatedwith a particular color pixel to be projected are then derived asfollow. At block 502, for a color video file to be projected onto thescreen 14, the logic moves to block 504 to derive a grayscale file fromthe color video file. The grayscale file may be derived on apixel-by-pixel basis.

Any appropriate method may be used for deriving a grayscale file from acolor file such that the grayscale values in the grayscale file aresynchronized with the color values in the color file using, e.g., timinginformation carried over from the color file into the grayscale file.

As examples, a grayscale value can be derived as follows for each colorpixel to be projected.

In systems in which luminance is directly indicated in the pixel data,that luminance may be used as the grayscale value.

When the pixel data indicates only color values for red, green, and blue(RGB), the corresponding grayscale value to be inserted into thegrayscale file can use weighted sums calculated from the RGB values, ifdesired after the gamma compression function has been removed first viagamma expansion.

In some embodiments, gamma expansion may be defined as:

-   -   C_\mathrm{linear}=\begin{cases}\frac{C_\mathrm{srgb}}{12.92}, &        C_\mathrm{srgb}\1e0.04045\\        \left(\frac{C_\mathrm{srgb}+0.055}{1.055}\right)^{2.4}, &        C_\mathrm{srgb}>0.04045 \end{cases}

where Csrgb represents any of the three gamma-compressed sRGB primaries(Rsrgb, Gsrgb, and Bsrgb, each in range [0,1]) and Clinear is thecorresponding linear-intensity value (R, G, and B, also in range [0,1]).

Then, luminance can be calculated as a weighted sum of the threelinear-intensity values. The sRGB color space is defined in terms of theCIE 1931 linear luminance Y, which is given byY=0.2126R+0.7152G+0.0722B.[5]

The coefficients represent the measured intensity perception of typicaltrichromat humans, depending on the primaries being used; in particular,human vision is most sensitive to green and least sensitive to blue. Toencode grayscale intensity in linear RGB, each of the three primariescan be set to equal the calculated linear luminance Y (replacing R,G,Bby Y,Y,Y to get this linear grayscale). Linear luminance typically needsto be gamma compressed to get back to a conventional non-linearrepresentation.

In contrast, for images in color spaces such as Y′UV and its relatives,which are used in standard color TV and video systems such as PAL,SECAM, and NTSC, a nonlinear luma component (Y′) can be calculateddirectly from gamma-compressed primary intensities as a weighted sum,which can be calculated quickly without the gamma expansion andcompression used in colorimetric grayscale calculations. In the Y′UV andY′IQ models used by PAL and NTSC, the grayscale component can becomputed asY′=0.299R′+0.587G′+0.114B′

where the prime distinguishes these gamma-compressed values from thelinear R, G, B, and Y discussed above.

Yet again, for the ITU-R BT.709 standard used for HDTV developed by theATSC, the grayscale value “Y′” can be calculated as:Y′=0.2126R′+0.7152G′+0.0722B′.

Although these are numerically the same coefficients used in sRGB above,the effect is different because they are being applied directly togamma-compressed values.

Recall that each color pixel to be projected is associated with pluralscreen pixels. Accordingly, once a single grayscale value is establishedfor each color pixel to be projected, the process then uses thatgrayscale value to establish screen pixel control data defining theconfiguration of each of the plural screen pixels associated with therespective color pixel to be projected. Thus, each grayscale value maybe expanded into “N” screen pixel control values to establish, for eachscreen pixel in the group of “N” screen pixels associated with the colorpixel to be projected from whence the grayscale value was derived,whether that screen pixel is to be controlled to be white or black.

In one embodiment, this is done using stippling or stippling-liketechniques, in which for lighter grayscale values, more of the screenpixels are caused to present a white appearance, and for darkergrayscale values, more of the screen pixels are caused to present ablack appearance, sometimes using randomly-selected pixels from amongthe group of screen pixels.

As additional illustrative examples of stippling-like techniques,halftoning or dithering may be used to configure the plural screenpixels associated with the respective color pixel to be projected toestablish the derived grayscale value. Example non-limiting details ofsuch techniques may be found in, e.g., Martin et al., “Scale-Dependentand Example-Based Stippling”, Computers & Graphics, 35(1):160-174 (2011)and Salomon, “The Computer Graphics Manual” (Springer-Verlag London,Ltd., 2011), both of which are incorporated herein by reference.

Note that the grayscale file may contain either one or both of thegrayscale values corresponding to a single color pixel to be projected.

In cases in which the refresh rate of the color video is faster than therefresh rate afforded by the active screen, each grayscale value may bean average of multiple color video values for the associated color pixelto be projected during a single cycle of screen refresh to which thegrayscale value applies. For example, if the screen is refreshed 30times per second and the color video is refreshed 60 times per second,each grayscale value may be the average of the two grayscale valuesderived from the two color pixels to be projected during the singlescreen refresh period. Or, each grayscale value may be a selected one ofthe multiple color video values for the associated color pixel to beprojected during a single cycle of screen refresh to which the grayscalevalue applies.

While a 4K screen is mentioned above, it is to be understood that otherscreen resolutions are encompassed by present principles. For example,individual pixels can be increased on the screen for 8K or higherprojection systems or combined to a visually equivalent e-ink contrastgrid that allows for larger grayscale areas or blocks. This couldhappen, for instance, when a 4K projection is presented on a very largescreen. The combination of the screen size and the projection resolutioninfluences the size of the matching grayscale contrast areas or blocksof e-ink on the screen. Moreover, the e-ink areas can be adjusted forpixel aspect ratios of different sizes, such as square versusrectangular. The e-ink pixel area shape and size can be tailored to howthe color video to be projected is shot, e.g., either as DV or intendedfor film.

The above methods may be implemented as software instructions executedby a processor, including suitably configured application specificintegrated circuits (ASIC) or field programmable gate array (FPGA)modules, or any other convenient manner as would be appreciated by thoseskilled in those art. Where employed, the software instructions may beembodied in a device such as a CD Rom or Flash drive or any of the abovenon-limiting examples of computer memories that are not transitorysignals. The software code instructions may alternatively be embodied ina transitory arrangement such as a radio or optical signal, or via adownload over the internet.

It will be appreciated that whilst present principals have beendescribed with reference to some example embodiments, these are notintended to be limiting, and that various alternative arrangements maybe used to implement the subject matter claimed herein.

What is claimed is:
 1. Apparatus comprising: at least one projectionscreen; at least one computer memory that is not a transitory signal andthat comprises instructions executable by at least one processor to:establish, for at least some pixels of at least some frames of a colorvideo file, respective grayscale values; using each one of at least someof the grayscale values, establish plural screen pixel control values,each screen pixel control value defining whether an associated screenpixel is to be configured to present a white appearance or a blackappearance, such that each of at least some pixels in the color videofile is associated with plural screen pixel control values; arrange thegrayscale values and/or the screen pixel control values in a grayscalefile in synchronization with the frames of the color video file fromwhence the grayscale values were derived; render the color video fileaccessible for projection onto the projection screen; and render thegrayscale file accessible to the the projection screen for control ofscreen pixels in the projection screen responsive to the screen pixelcontrol values.
 2. The apparatus of claim 1, comprising the at least oneprocessor.
 3. The apparatus of claim 1, wherein the screen pixel controlvalues for each grayscale value are established using a stippling-liketechnique.
 4. The apparatus of claim 1, wherein the grayscale file andcolor video file are both sourced from a single source.
 5. The apparatusof claim 1, wherein the color video file is sent from a first source toa projector for projection onto the projection screen, and the grayscalefile is sent from a second source to the projection screen.
 6. Theapparatus of claim 1, wherein the grayscale values are established usingluminance information in the color video file.
 7. The apparatus of claim1, wherein the instructions are executable for establishing, for allpixels of at least some frames of the color video file, respectivegrayscale values, and using each one of all of the grayscale values toestablish plural screen pixel control values.
 8. The apparatus of claim1, wherein the projection screen is an e-ink screen.
 9. Apparatuscomprising: at least one active screen; at least one computer memorythat is not a transitory signal and that comprises instructionsexecutable by at least one processor to: associate respective groups ofplural screen pixels of the active screen with respective individualcolor pixels from a projector to be projected onto the active screen;and in synchronization with projection of the color pixels onto theactive screen, control the respective plural screen pixels of each of atleast some of the respective individual color pixels to establish ademanded grayscale on the active screen.
 10. The apparatus of claim 9,wherein the instructions are executable to: establish, for at least somepixels of at least some frames of a color video file, respectivegrayscale values; using each one of at least some of the grayscalevalues, establish plural screen pixel control values, each screen pixelcontrol value defining whether an associated screen pixel is to beconfigured to present a white appearance or a black appearance, suchthat each of at least some pixels in the color video file is associatedwith plural screen pixel control values.
 11. The apparatus of claim 10,wherein the instructions are executable to: arrange the grayscale valuesand/or the screen pixel control values in a grayscale file insynchronization with the frames of the color video file from whence thegrayscale values were derived.
 12. The apparatus of claim 11, whereinthe instructions are executable to: render the color video fileaccessible for projection onto the active screen; and render thegrayscale file accessible to the active screen for control of screenpixels in the active screen responsive to the screen pixel controlvalues.
 13. The apparatus of claim 10, wherein the screen pixel controlvalues for each grayscale value are established using a stippling-liketechnique.
 14. The apparatus of claim 10, wherein the grayscale valuesare established using luminance information in the color video file. 15.The apparatus of claim 9, comprising the at least one processor.
 16. Theapparatus of claim 9, wherein the instructions are executable to:associate the respective groups of plural screen pixels in the activescreen with the respective individual color pixels by: projecting atleast one column and/or row of color pixels onto the screen; andactivating at least plural columns and/or rows of screen pixels.
 17. Theapparatus of claim 16, wherein the instructions are executable to: basedon at least one image of the at least one column and/or row of colorpixels projected onto the screen over activated columns and/or rows ofscreen pixels, associating respective groups of plural screen pixelswith the respective individual color pixels.
 18. The apparatus of claim9, wherein the instructions are executable to align at least one edge ofat least one frame of color pixels with at least one corresponding edgeof the active screen.
 19. A method comprising: on at least one computerstorage, associating plural screen pixels with respective individualpixels to be projected; using at least one projector, projecting thepixels to be projected onto a screen associated with the screen pixelsto produce a demanded color image; and using at least one processor,controlling the screen pixels to produce a demanded grayscale derivedfrom the respective pixels to be projected.
 20. The method of claim 19,comprising: arranging grayscale values and/or screen pixel controlvalues in a grayscale file in synchronization with frames of a colorvideo file from whence the grayscale values were derived, the colorvideo file including values representing the individual pixels to beprojected.